We present evidence of land-level change resulting from the 2016 M_w 7.6 Chiloé earthquake from tidal wetlands along the southern coastline of Isla de Chiloé, Chile, to test criteria for the detection of low-level, <0.1 m, coseismic land-level change. In order to record coseismic land-level change in tidal wetland sediments, both the creation and preservation thresholds must be exceeded. High-resolution diatom analyses of sediment blocks at two tidal marshes reveal that the 2016 earthquake exceeded the creation threshold and a statistically significant change in diatom assemblage is recorded. In contrast, the preservation threshold was not exceeded and the record of coseismic land-level motion is not preserved at any location visited. After nine months, interseismic and coseismic changes are statistically indistinguishable. The most sensitive part of the tidal wetland is not consistent between research locations, possibly as a result of changes in sedimentation after the earthquake. We compare records of change from great earthquakes in Alaska with the record from the Chiloé earthquake to explore the detection limit. We propose that coastal palaeoseismological records are highly likely to underestimate the frequency of major (M_w 7–8) earthquakes, with important implications for recurrence intervals and assessment of future seismic hazards.

中文翻译：

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潮汐沼泽作为大型逆冲地震记录器的敏感性：来自 2016 年 12 月 25 日 Mw 7.6 Chiloé 地震的限制，智利

我们提供了由 2016 M _w引起的土地水平变化的证据7.6 智利奇洛埃岛南部海岸线潮汐湿地的奇洛埃地震，以测试检测低水平、<0.1 m、同震地平面变化的标准。为了记录潮汐湿地沉积物的同震地平面变化，必须超过创建和保存阈值。对两个潮汐沼泽地沉积物块的高分辨率硅藻分析表明，2016 年地震超过了创建阈值，并记录了硅藻组合的统计显着变化。相比之下，没有超过保存阈值，并且在任何访问的位置都没有保存同震地平面运动的记录。九个月后，地震间和同震变化在统计上无法区分。潮汐湿地最敏感的部分在研究地点之间并不一致，可能是地震后沉积变化的结果。我们将阿拉斯加大地震的变化记录与奇洛埃地震的记录进行比较，以探索检测极限。我们建议沿海古地震记录很可能低估了大地震的频率（M_w 7–8) 地震，对重复间隔和未来地震灾害的评估具有重要意义。